Repair of dual walled metallic components using braze material

ABSTRACT

A dual walled component includes a spar comprising a plurality of pedestals; a coversheet attached to a first set of pedestals from the plurality of pedestals; and a repaired coversheet portion attached to a second set of pedestals from the plurality of pedestals and to the coversheet, where the repaired coversheet portion includes a braze material.

This application is a continuation of U.S. patent application Ser. No.16/984,624, filed Aug. 4, 2020, which is a divisional of U.S. patentapplication Ser. No. 15/053,082, filed Feb. 25, 2016, now U.S. Pat. No.10,766,105, which claims the benefit of U.S. Provisional Application No.62/121,269, filed Feb. 26, 2015. The entire contents of each of theseapplications are incorporated herein by reference.

TECHNICAL FIELD

The disclosure relates to techniques for repairing dual walled metalliccomponents using a braze material.

BACKGROUND

Dual walled components may be used in high temperature mechanicalsystems, such as gas turbine engines. A dual walled component mayinclude a spar, which provides structural support and is the main loadbearing element of the dual walled component. The spar may include aplurality of pedestals to which a coversheet or outer wall is attached.The coversheet defines the outer surface of the dual walled component,and may function as a heat shield. Cooling fluid, such as air, may bepassed through the volume between the spar and the back side of thecoversheet to aid in cooling the coversheet. Due to this back sidecooling, dual walled components may allow use of higher operatingtemperatures than single walled components.

SUMMARY

In some examples, the disclosure described a method for repairing a dualwalled component comprising a spar comprising a plurality of pedestalsand a coversheet attached to the plurality of pedestals. The method mayinclude removing a damaged portion of the coversheet from the dualwalled component to expose a plurality of exposed pedestals and define arepair location and an adjacent coversheet portion. The method also mayinclude filling space between the plurality of exposed pedestals with astop material, wherein the stop material defines a surface substantiallyaligned with a pedestal-contacting surface of the adjacent coversheetportion. In some examples, the method additionally includes positioninga braze material on the surface of the stop material and attaching thebraze material to the plurality of exposed pedestals and adjacentcoversheet portion to form a repaired coversheet portion.

In some examples, the disclosure describes a dual walled component thatincludes a spar including a plurality of pedestals, a coversheetattached to a first set of pedestals from the plurality of pedestals,and a repaired coversheet portion attached to a second set of pedestalsfrom the plurality of pedestals and to the coversheet. The repairedcoversheet portion includes a braze material.

The details of one or more examples are set forth in the accompanyingdrawings and the description below. Other features, objects, andadvantages will be apparent from the description and drawings, and fromthe claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a flow diagram illustrating an example technique for repairinga dual walled component using a braze material.

FIG. 2 is an exploded sectional view of an example dual walled componentincluding a coversheet and a spar.

FIG. 3 is a conceptual and schematic diagram illustrating an exampledamaged dual walled component.

FIG. 4 is a conceptual and schematic diagram illustrating an exampledual walled component after a damaged portion has been removed.

FIG. 5 is a conceptual and schematic diagram illustrating an exampledual walled component after a damaged portion has been removed andspaces around pedestals filled with stop material.

FIG. 6 is a conceptual and schematic diagram illustrating an exampledual walled component after a damaged portion has been removed, spacesaround pedestals have been filled with stop material, and braze materialhas been introduced to a repair location.

FIG. 7 is a conceptual and schematic diagram illustrating an exampledual walled component including a portion that has been repaired using abraze material.

DETAILED DESCRIPTION

The disclosure describes techniques for repairing a dual walledcomponent using a braze patch. As described above, a dual walledcomponent includes a spar and a coversheet or outer wall. The spar mayinclude a plurality of pedestals to which the coversheet is attached.

Although the dual walled component may allow use of high temperaturesdue to the cooling provided by the back side cooling channels, thecoversheet may be relatively thin. Because of this, the coversheet maybe relatively easily damaged, e.g., by mechanical impact or chemicalreaction with species in the operating environment, such ascalcia-magnesia-alumina-silicate (CMAS). Further, because the coversheetis relatively thin and the pedestals are relatively small (e.g.,thousandths of an inch), repair of the coversheet may be relativelydifficult. Hence, some damaged dual walled components may be discardedrather than repaired.

In accordance with examples of this disclosure, a braze material may beused to repair the coversheet and, in some examples, the pedestals of adual walled component. For example, a portion of a coversheet may bedamaged by mechanical impact with an object or reaction with a chemicalspecies in the operating environment of the dual walled component. Thedamaged portion may be removed along with, in some examples, part of anundamaged portion of the coversheet adjacent to the damaged portion todefine a repair location. Removing the damaged portion of the coversheetmay expose some pedestals of the spar. A braze material then may beattached to the plurality of exposed pedestals and adjacent coversheetand form a repaired coversheet portion.

In some examples, space between the plurality of exposed pedestals maybe filled with a stop material. The stop material may define a surfacesubstantially aligned with a pedestal-contacting surface of the adjacentcoversheet portion, so that an inner surface (a surface toward thepedestals) of the repaired coversheet portion will be substantiallyaligned with the inner (pedestal-contacting) surface of the adjacentcoversheet portion. After the stop material is filled in the space,braze material, either in the form of a braze preform or a braze pastemay be positioned on the surface of the stop material and adjacent tothe exposed pedestals and adjacent coversheet, to form the repairedcoversheet portion attached to the exposed pedestals and the adjacentcoversheet. The braze material then may be heated to join the brazematerial to the exposed pedestals and adjacent coversheet. In this way,the techniques described herein may be used to repair a dual walledcomponent with a braze material.

FIG. 1 is a flow diagram illustrating an example technique for repairinga dual walled component using a braze material. The technique of FIG. 1will be described with concurrent reference to the conceptual diagramsof FIGS. 2-7 for purposes of illustration only. However, it will beunderstood that in other examples, the technique of FIG. 3 may be usedto repair other dual walled components, or both.

FIG. 2 is an exploded sectional view of an example dual walled component30 including a coversheet 32 and a spar 34, which may be repaired with abraze material using the technique illustrated in FIG. 1 . Coversheet 32and spar 34 may be joined using brazing or diffusion bonding. In theexample of FIG. 2 , dual walled component 30 is an airfoil for a gasturbine engine. In other examples, dual walled component repaired with abraze material using the technique illustrated in FIG. 1 may be acombustor liner or the like. Each of coversheet 32 and spar 34 arepreformed, and may be cast or wrought. In the example of FIG. 2 ,coversheet 32 includes a plurality of members (e.g., four members). Inother examples, coversheet 32 may include more or fewer members.

Coversheet 32 is shaped to substantially correspond to an outer surfaceof spar 34. In some examples, coversheet 32 and spar 34 may be formed ofsimilar materials, such as similar alloys. In other examples, coversheet32 and spar 34 may be formed of different materials, selected to providedifferent properties. For example, spar 34 may be formed of a materialselected to provide strength to dual walled component 30, whilecoversheet 32 is formed of a material selected to provide resistance tooxidation or a relatively low coefficient of thermal expansion. In someexamples, the alloys from which coversheet 32 and spar 34 are formed mayinclude a Ni-based alloy, a Co-based alloy, a Ti-based alloy, or thelike.

Spar 34 may also include a plurality of pedestals on an outer surface ofthe walls of spar 34, to which coversheet 32 are joined. The pluralityof pedestals may help define channels between spar 34 and coversheet 32through which cooling fluid (e.g., air) may flow. In some examples,coversheet 32 and spar 34 include one or more locating features 38including protrusion 40 of coversheet 32 and complementary depression 42of spar 34. The locating features 38 may assist with positioningcoversheet 32 relative to spar 34.

FIG. 3 is a conceptual and schematic diagram illustrating an exampledual walled component 52 that is damaged. As shown in FIG. 3 , a dualwalled component 52 includes a spar 54, which defines an inner wall ofdual walled component 52 and includes a plurality of pedestals 56. Acoversheet 58 or outer wall is attached to plurality of pedestals 56. Insome examples, each of plurality of pedestals 56 may define a height ofbetween about 0.005 inch (about 0.127 mm) and about 0.040 inch (about1.016 mm). In some examples, a spacing between adjacent pedestals ofplurality of pedestals 56 may be between about 0.015 inch (about 0.381mm) and about 0.020 (about 0.508 mm).

In some examples, an external surface (opposite plurality of pedestals56) of coversheet 58 may coated with a coating 60, which may include,for example, a thermal barrier coating. A thermal barrier coating mayinclude a bond coat on coversheet 58 and a thermally insulative layer onthe bond coat. The thermally insulative layer may include, for example,yttria or hafnia partially or fully stabilized with a rare earth oxide,such as yttria.

Coversheet 58 also may include a plurality of film cooling holes 62.Each of plurality of film cooling holes 62 may extend from an outersurface to an inner surface of coversheet 58. Each of plurality of filmcooling holes 62 fluidically connects to a cavity defined by coversheet58 and spar 54. Cooling fluid, such as air, may flow through the cavityand exit through film cooling holes 62 to help cool coversheet 58.

Damaged dual walled component 52 includes a damaged portion 64. In theexample illustrated in FIG. 3 , damaged portion 64 extends through thethickness of coversheet 58 and includes a portion of one of theplurality of pedestals 56. In other examples, damaged portion 64 mayextend only partially through the thickness of coversheet 58, may notinclude a portion of one of the plurality of pedestals 56, or both.Damaged portion 64 may be due to mechanical impact, chemical reactionwith an environmental species, or the like.

As described briefly above, the braze material used in the repairtechnique illustrated in FIG. 1 may include a braze preform, powder,paste, tape, rod, ribbon, wire, or the like. In some examples in whichthe braze material includes a braze preform, the technique of FIG. 1optionally may include forming a braze preform (12). In some examples,the braze preform may be formed from a larger part using a machiningprocess, such as an adaptive machining technique. In an adaptivemachining technique, a non-contact technique may be used to inspectdamaged portion 64 and, optionally, an adjacent portion of coversheet58, to obtain dimensional surface data of damaged portion 64. In someexamples, the non-contact technique may utilize a coordinate measuringmachine (CMM) that determines coordinates of points at multiplelocations of damaged portion 64, and, optionally, an adjacent portion ofcoversheet 58. The measured dimensional surface data can include anynumber, or set or multiple sets, of point coordinates that thenon-contact technique indicates are on the surface of damaged portion64, and, optionally, an adjacent portion of coversheet 58, at various(different) locations. As will be appreciated, the greater the number ofpoints, which can be in the hundreds to millions or more, in a set ormultiple sets, the more robust the measured dimensional surface datawill be in establishing the shape (and location) of damaged portion 64,and, optionally, an adjacent portion of coversheet 58.

The measured dimensional surface data then can be compared to surfacemodel data of dual walled component 52, or at least the portion ofcoversheet 58 that includes damaged portion 64, and, optionally, theadjacent portion of coversheet 58 to generate a compromise surfacemodel. The surface model data can include any suitable mathematicalmodel, for example, in the form of one or more curves or surfaces,including splines or non-uniform rational basis splines (NURBS), forexample, that represent (model) the airfoil spar surface. In someexamples, the surface model data can include a design intent surface ofdual walled component 52, defined by, for example, CAD spline knots. Insome examples, the design intent surface can represent the ideal surfaceof dual walled component 52, that is the “perfect world” representationof the component surface, before, for example, the consideration oftolerances, and before the damage to coversheet 58 that resulted indamaged portion 64.

In some examples, the surface model data may be modified to arrive atthe compromise surface model by performing a six degree of freedom (DOF)best-fit of surface model data to the measured dimensional surface data.In some examples, the surface model data may be best-fit to the measureddimensional surface data to account for possible misalignment caused by,for example, uncertainty in the orientation of dual walled component 52during measurement of the dimensional surface data. Alternatively, themeasured dimensional surface data may be best-fit to the surface modeldata to arrive at the compromise surface model.

In some examples, the compromise surface model may be determined usingany suitable numerical analysis. For example, a weighted nonlinear leastsquares minimization to rotate and translate the surface model data toarrive at the compromise surface model. Further, any suitable techniquesfor solving multidimensional nonlinear problems can be employed;non-limiting examples include Newton-Raphson, sequentialover-relaxation, genetic algorithms, gradient methods, among others.

In some examples, when determining the compromise surface model, thegeometry of damaged portion 64 may be discarded, as the geometry ofdamaged portion 64 may deviate so significantly from the surface modeldata to be unrepresentative of the original shape of coversheet. In somesuch examples, the measured dimensional data of the adjacent portion ofcoversheet 58 may be compared to the surface model data to arrive at acompromise surface model for that portion of the braze preform, and thesurface model data may be used for the compromise surface model fordamaged portion 64.

Once the compromise surface model has been determined, a sintered brazematerial may be machined to define the braze preform. In other examples,adaptive machining may not be used to form the braze preform, and thebraze preform may have a shape defined by the model surface data or ageneric shape (e.g., a sheet). In still other examples, the technique ofFIG. 1 may not including forming a braze preform (12).

The technique of FIG. 1 includes removing damaged portion 64 of dualwalled component 52 (14). The resulting dual walled component 52 withdamaged portion 64 removed is shown in FIG. 4 . In some examples,removing the damaged portion 64 of dual walled component 52 (14) mayinclude removing at least part of coating 60 on at least damaged portion64 of dual walled component 52. In some examples, coating 60 may beremoved from all of dual walled component 52. In other examples, coating60 may be removed from the damaged portion 64 and an adjacent portion ofcoversheet 58, but not all of dual walled component 52. For example, asshown in FIG. 4 , coating 60 may be removed to uncover part of outersurface 76 of coversheet 58. This may facilitate repair of coversheet 58(e.g., joining of material to coversheet 58) and subsequent working ofthe repaired portion (e.g., machining the repaired portion to smooth theinterface between the repaired portion and coversheet 58).

Removing damaged portion 64 (14) may include the damaged portion 64 ofthe coversheet 58, and, in some examples, an undamaged adjacent portionof coversheet 58, as shown in FIG. 4 . By removing the undamagedadjacent portion of coversheet 58, a clean and undamaged portion ofcoversheet 58 may be exposed, which may facilitate attaching thematerial forming the repaired coversheet portion to the remainder ofdual walled component 52.

In some examples, in addition to coversheet 58 being damaged, at leastsome of the plurality of pedestals 56 may be damaged, as shown in FIG. 3. Hence, in some examples, removing damaged portion 64 of dual walledcomponent 52 (14) may include removing at least the damaged portions ofany damaged pedestals 56.

Removing damaged portion 64 of dual walled component 52 (14) may includeusing mechanical techniques, such as grinding, drilling, cutting, or thelike to remove the damaged portion 64. Removing damaged portion 64 ofdual walled component 52 (14) may define a repair location 74 (FIG. 4 )and an adjacent coversheet portion, and may expose one or more exposedpedestals 78 that were underlying damaged portion 64 of coversheet 58.Removing damaged portion 64 of dual walled component 52 (14) may leavethe internal structure of dual walled component 52, including thegeometry of cooling channels defined by spar 54 and pedestals 56substantially intact.

The technique of FIG. 1 also includes filling a cavity between pedestals56 and 78 with stop material 82 (FIG. 5 ) (16). For example, a cavitybetween exposed pedestal 78 and adjacent pedestals 56 may be filled withstop material 82 such that an outer surface of the stop material 82 issubstantially aligned with an inner surface of the adjacent portions ofcoversheet 58.

Stop material 82 may include a high melting temperature refractivematerial that does not react with adjacent portions of dual walledcomponent 52 (e.g., exposed pedestal 78, plurality of pedestals 56, spar54, and/or coversheet 58). For example, the high melting temperaturerefractive material may have a melting temperature greater than thetemperature at which the braze material is heated to join the brazematerial to coversheet 58 and exposed pedestal 78. For example, stopmaterial 82 may include an oxide, such as yttrium oxide, aluminum oxide,or the like, mixed with a binder. The binder may include, for example, awater- or alcohol-based binder. In some examples, stop material 82 thatincludes an oxide and a binder may be in the form of a tape, a preform,a rope, a powder, or the like.

In other examples, stop material 82 may include a refractory metal, suchas molybdenum; or the like. The refractory metal may be in the form of asheet or other preform. In some examples, the tape, preform, or rope maybe shaped to define the outer surface of stop material 82 substantiallyaligned with an inner surface of the adjacent portions of coversheet 58and, if applicable, to help define a shape of any portions of exposedpedestal 78 to be repaired. Alternatively or additionally, the tape,preform, or rope may be shaped to define the outer surface of stopmaterial 82 substantially aligned with tops of undamaged exposedpedestals.

The technique of FIG. 1 also may include attaching braze material tocoversheet 58 and at least one exposed pedestal 78 (18). In someexamples, attaching braze material to coversheet 58 and at least oneexposed pedestal 78 (18) may first includes positioning the brazematerial 92 on stop material 82 in repair location 74, as shown in FIG.6 .

In some examples, the braze material may include a braze preform. Thebraze preform may define a shape that substantially conforms to theshape of the portion of coversheet 58 that was removed when removingdamaged portion 64. A braze preform may reduce shrinkage compared to abraze paste, and thus may improve a fit of braze material 92 tocoversheet 58. The braze preform may be positioned on stop material 82by placing the braze preform at repair location 74.

In other examples, braze material 92 may include a powder, a paste(e.g., powder carried by a solvent), a rod, a ribbon, a wire, or thelike. Braze material 92 may not be preformed to substantially conform tothe shape of the portion of coversheet 58 that was removed when removingdamaged portion 64. Braze material 92 may be positioned using any of avariety of techniques, including, for example, spreading; dispensingwith a syringe; positioning individual ribbons, wires, or rods; or thelike. In some examples, after positioning braze material 92, the brazematerial 92 may substantially conform to the shape of the portion ofcoversheet 58 that was removed when removing damaged portion 64, even ifbraze material 92 does not include a braze preform.

Braze material 92 may include any suitable braze composition, such as ametal or an alloy. For example, if coversheet 58 includes a Ni- orCo-based superalloy, braze material 92 may include a braze of similarcomposition. In other examples, braze material 92 may include an alloyhaving a different composition than coversheet 58. For example, damagedportion 64 may be have been damaged due to localized conditions, such ashigher temperatures, exposure to certain environmental contaminants, orhigher mechanical stresses, which are not common to all portions ofcoversheet 58. In some such examples, braze material 92 may include analloy having a composition selected to better resist the localizedconditions compared to the alloy from which the remainder of coversheet58 is formed. Regardless of the composition of braze material 92compared to coversheet 58, the composition of braze material 92 may beselected such that the coefficient of thermal expansion is sufficientlysimilar that thermal cycling of dual walled component 52 does not resultin sufficient levels of stress to cause of the interface betweencoversheet 58 and braze material 92 to crack or fail.

In some examples, braze material 92 may include a wide gap brazecomposition, which includes particles of a high temperature alloy withinmixed with a braze alloy comparable to the high temperature alloyconstituents. For example, a wide gap braze composition may include anickel-based braze mixed with particles of a nickel-based superalloy ora cobalt-based braze mixed with particles of a cobalt-based alloy.

Regardless of the braze material 92 used, attaching braze material 92 tocoversheet 58 and at least one exposed pedestal 78 (18) may also includeheating at least the braze material 92 to cause the braze material 92 tojoin to coversheet 58 and at least one exposed pedestal 78. For example,at least the braze material 92 may be heated to a temperature betweenabout 1,500° F. (about 815° C.) and about 2,400° F. (about 1315° C.) tocause the braze material 92 to join to coversheet 58 and at least oneexposed pedestal 78. In some examples, dual walled component 52 andbraze material 92 may be enclosed in a vacuum furnace, and both dualwalled component 52 and braze material 92 may be heated within thevacuum furnace. Vacuum brazing may result in substantial temperatureuniformity within dual walled component 52 and braze material 92, whichmay reduce residual stresses at the interface of dual walled component52 and braze material 92.

In some examples, induction heating may be used to heat braze material92. For example, induction heating may be substantially localized tobraze material 92, leaving substantially all of dual walled component ata lower temperature than the braze temperature. Localized heating ofbraze material 92 using induction heating may reduce dimensionalnonconformance of dual walled component 52, which may occur if all ofdual walled component 52 is heated during the brazing technique.

After formation of the repaired coversheet portion, stop material 82 maybe removed. For example, dual walled component 52 may be heated to heatstop material 82 in examples in which stop material 82 includes arefractory oxide and a binder. Stop material 82 may be heated to atemperature sufficient to burn the binder, creating a powder includingthe burned binder and the refractive oxide. This powder then may beremoved, e.g., by flowing a pressurized fluid through the cavitiesbetween coversheet 58 and spar 74. In other examples, such as examplesin which stop material 82 includes a refractory metal, a chemicaletching technique may be used to remove stop material 82. The etchantmay be selected to react with the refractory metal while not reactingwith the parts of dual walled component 52.

FIG. 7 is a conceptual and schematic diagram illustrating dual walledcomponent 52 including a repaired coversheet portion 82 that has beenrepaired using braze material 92. Repaired coversheet portion 82 may beattached to any exposed pedestals 78 and portions of coversheet 58adjacent to repair location 74.

As shown in FIG. 7 , in some examples, repaired coversheet portion 82may substantially conform to the shape of the previous coversheet inrepair location 74 and may include an outer surface that issubstantially aligned with the outer surface of coversheet 58. In someexamples, this may be the result of using a braze preform.

Additionally or alternatively, the technique of FIG. 1 may includemachining repaired coversheet portion 82 (20). For example, grinding,polishing, or other machining techniques may be used to smooth theinterface between repaired coversheet portion 82 and coversheet 58. Insome examples, an adaptive machining technique may be utilized todetermine the machining to be performed to smooth the interface betweenrepaired coversheet portion 82 and coversheet 58.

In an adaptive machining technique, a non-contact technique may be usedto inspect repaired coversheet portion 82 and, optionally, an adjacentportion of coversheet 58, to obtain dimensional surface data of repairedcoversheet portion 82. In some examples, the non-contact technique mayutilize a coordinate measuring machine (CMM) that determines coordinatesof points at multiple locations of repaired coversheet portion 82, and,optionally, an adjacent portion of coversheet 58. The measureddimensional surface data can include any number, or set or multiplesets, of point coordinates that the non-contact technique indicates areon the surface of repaired coversheet portion 82, and, optionally, anadjacent portion of coversheet 58, at various (different) locations. Aswill be appreciated, the greater the number of points, which can be inthe hundreds to millions or more, in a set or multiple sets, the morerobust the measured dimensional surface data will be in establishing theshape (and location) of repaired coversheet portion 82, and, optionally,an adjacent portion of coversheet 58.

The measured dimensional surface data then can be compared to surfacemodel data of dual walled component 52, or at least the portion ofcoversheet 58 that includes repaired coversheet portion 82, and,optionally, the adjacent portion of coversheet 58 to generate acompromise surface model. The surface model data can include anysuitable mathematical model, for example, in the form of one or morecurves or surfaces, including splines or non-uniform rational basissplines (NURBS), for example, that represent (model) the airfoil sparsurface. In some examples, the surface model data can include a designintent surface of dual walled component 52, defined by, for example, CADspline knots. In some examples, the design intent surface can representthe ideal surface of dual walled component 52, that is the “perfectworld” representation of the component surface, before, for example, theconsideration of tolerances.

In some examples, the surface model data may be modified to arrive atthe compromise surface model by performing a six degree of freedom (DOF)best-fit of surface model data to the measured dimensional surface data.In some examples, the surface model data may be best-fit to the measureddimensional surface data to account for possible misalignment caused by,for example, uncertainty in the orientation of dual walled component 52during measurement of the dimensional surface data. Alternatively, themeasured dimensional surface data may be best-fit to the surface modeldata to arrive at the compromise surface model.

In some examples, the compromise surface model may be determined usingany suitable numerical analysis. For example, a weighted nonlinear leastsquares minimization to rotate and translate the surface model data toarrive at the compromise surface model. Further, any suitable techniquesfor solving multidimensional nonlinear problems can be employed;non-limiting examples include Newton-Raphson, sequentialover-relaxation, genetic algorithms, gradient methods, among others.

Once the compromise surface model has been determined, repairedcoversheet portion 82 and adjacent portions of coversheet 58 may bemachined based on the compromise surface data.

In some examples, the technique of FIG. 1 may optionally include formingcoating 60 on repaired coversheet portion 82 and any other exposed outersurface of coversheet 58 (22). In some examples, coating 60 on repairedcoversheet portion 82 may be the substantially the same as (e.g., thesame as or nearly the same as) coating 60 on coversheet 58. In otherexamples, coating 80 on repaired coversheet portion 82 may be differentthan coating 60 on coversheet 58. Regardless, in some examples, coating60 may be a thermal barrier coating and may include a bond layer and atleast one thermally insulative layer.

In some examples, the technique of FIG. 1 may optionally include formingfilm cooling holes 62 in repaired coversheet portion 82 (24). Formingfilm cooling holes 562 may utilize mechanical working, such as drilling,energy drilling, such as laser drilling, or the like. In some examples,film cooling holes 62 may be formed at locations corresponding tolocations of previous cooling holes in damaged portion 64. In this way,the technique of FIG. 1 may utilize a braze material to repaircoversheet 58 and, optionally, at least one pedestal of plurality ofpedestals 56.

As will be appreciated, in these ways a braze material may be used torepair coversheets and, optionally, pedestals of dual walled components,such as combustor liners or gas turbine engine blades. This mayfacilitate repair of dual walled components rather than requiringdamaged dual walled components to be discarded and replaced with newdual walled components, thus providing cost savings.

Various examples have been described. These and other examples arewithin the scope of the following claims.

1. A dual walled component comprising: a spar comprising a plurality ofpedestals; a coversheet attached to a first set of pedestals from theplurality of pedestals; a repaired coversheet portion attached to thecoversheet and a second set of pedestals from the plurality ofpedestals; and a coating comprising: a first portion overlying thecoversheet; and a second portion overlying the repaired coversheetportion.
 2. The dual walled component of claim 1, wherein the firstportion of the coating overlies a first portion of the coversheet, andwherein the second portion of the coating overlies the repairedcoversheet portion and a second portion of the coversheet.
 3. The dualwalled component of claim 1, wherein the coating comprises a thermalbarrier coating.
 4. The dual walled component of claim 3, wherein thethermal barrier coating comprises a bond coat and at least one thermallyinsulative layer on the bond coat.
 5. The dual walled component of claim4, wherein the at least one thermally insulative layer comprises atleast one of yttria partially or fully stabilized with a rare earthoxide or hafnia partially or fully stabilized with a rare earth oxide.6. The dual walled component of claim 1, wherein a composition of thefirst portion of the coating is substantially the same as a compositionof the second portion of the coating.
 7. The dual walled component ofclaim 1, wherein a composition of the first portion of the coating isdifferent from a composition of the second portion of the coating. 8.The dual walled component of claim 1, wherein the repaired coversheetportion comprises at least one of a braze alloy or a wide gap brazealloy derived from a braze material.
 9. The dual walled component ofclaim 8, wherein the repaired coversheet portion comprises the wide gapbraze alloy derived from the braze material, and wherein the brazematerial comprises a braze preform.
 10. The dual walled component ofclaim 1, wherein the coversheet comprises a first alloy, and wherein therepaired coversheet portion comprises a second alloy different from thefirst alloy.
 11. The dual walled component of claim 1, wherein the spar,the coversheet, and the repaired coversheet portion define at least aportion of a component of a gas turbine engine.
 12. The dual walledcomponent of claim 1, wherein the coversheet defines an outer wall ofthe dual walled component.
 13. The dual walled component of claim 1,wherein the repaired coversheet portion comprises a Ni-base alloy, aCo-based alloy, or a Ti-based alloy.
 14. A method for repairing a dualwalled component, comprising: removing a damaged portion of a coversheetand a damaged portion of a coating overlying the coversheet from a dualwalled component to define a repair location and an adjacent coversheetportion, wherein the dual walled component comprises: a spar comprisinga plurality of pedestals, wherein a second set of pedestals of theplurality of pedestals are exposed; the coversheet attached to a firstset of pedestals from the plurality of pedestals; and a first portion ofthe coating overlying the adjacent coversheet portion; forming arepaired coversheet portion on the second set of pedestals; and forminga second portion of the coating on the repaired coversheet portion. 15.The method of claim 14, wherein the adjacent coversheet portion is afirst portion of the coversheet, wherein the repair location includes asecond portion of the coversheet, and wherein the second portion of thecoating overlies the repaired coversheet portion and the second portionof the coversheet.
 16. The method of claim 14, wherein forming therepaired coversheet portion further comprises: filling space between thesecond set of pedestals with a stop material, wherein the stop materialdefines a surface substantially aligned with a pedestal-contactingsurface of the adjacent coversheet portion; positioning a braze materialon the surface of the stop material; and attaching the braze material tothe second set of pedestals and the adjacent coversheet portion.
 17. Themethod of claim 14, wherein the coating comprises a thermal barriercoating.
 18. The method of claim 17, wherein the thermal barrier coatingcomprises a bond coat and at least one thermally insulative layer on thebond coat.
 19. The method of claim 14, wherein a composition of thefirst portion of the coating is substantially the same as a compositionof the second portion of the coating.
 20. The method of claim 14,wherein a composition of the first portion of the coating is differentfrom a composition of the second portion of the coating.